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Old 05-04-2013, 03:23 PM
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Lead and valves

Guy I work for carried a pair of 289 heads to be worked. Dude told him that if he didn't install hardened seats, he's have to run a lead additive in the fuel from now on. Else they wouldn't last over 10,000 miles.
I've never heard of that, and have been running my vehicles with cast iron seats for many miles over 100k, without adding any lead to the gas.
Strange thing is that this 289 has about 120k on it, and only reason it's been torn down, is that it's set for about 12 years, then the oil pump quit when it was driven a short while. The teardown revealed why the pump quit, had nothing to do with fuel, but time sitting and rusting.

I remember back in the 70's how glad I was that they took the lead out of fuel. Made for fewer fouled plugs, and sticky valves.

I asked him why, he said that the unleaded fuel burns hotter, especially with ethanol in it. Huh!? I'm not certian that I believe that.
He allows that it will eat exhaust valves like popcorn. Sed he's had it happen in the past on other heads he's built. Hmmm.

I call BS. What say you?

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Old 05-04-2013, 04:11 PM
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Quote:
Originally Posted by st3gamefarm View Post
Guy I work for carried a pair of 289 heads to be worked. Dude told him that if he didn't install hardened seats, he's have to run a lead additive in the fuel from now on. Else they wouldn't last over 10,000 miles.
I've never heard of that, and have been running my vehicles with cast iron seats for many miles over 100k, without adding any lead to the gas.
Strange thing is that this 289 has about 120k on it, and only reason it's been torn down, is that it's set for about 12 years, then the oil pump quit when it was driven a short while. The teardown revealed why the pump quit, had nothing to do with fuel, but time sitting and rusting.

I remember back in the 70's how glad I was that they took the lead out of fuel. Made for fewer fouled plugs, and sticky valves.

I asked him why, he said that the unleaded fuel burns hotter, especially with ethanol in it. Huh!? I'm not certian that I believe that.
He allows that it will eat exhaust valves like popcorn. Sed he's had it happen in the past on other heads he's built. Hmmm.

I call BS. What say you?
I'm no engineer, and can only parrot what I have read or heard from engineers and others who have been there, done that.

Valve reversion into the seats has been explained to me thusly:
Years ago, tetraethyl lead was the cheapest fuel additive the refineries could add to gasoline to dirty-up the valve seats.

If you've done any welding at all, you will know that the joint needs to be clean in order for the weld to "take" on the material. If there is a foreign substance on the part to be welded, it won't work.

Many years ago, engineers discovered that due to extreme heat, the hot exhaust valve would "weld" a little to the seat when the valve closed. When the valve opened again, it would tear off a little of the seat where the weld had occurred. After a number of these tears, the valve would have cut a ring down into the seat and the motor would have to be disassembled to re-establish a valid seat on the valve and seat in order to accomplish compression. This was called valve reversion.

Someone, at some time in the past, discovered that if they added a substance to the fuel that would "dirty-up" the seat, then the valve could not weld to the seat and reversion could not occur. This substance was tetraethyl lead. This worked great for several decades, until the hippie movement in the 60's began to make all of us aware of the damage we were doing to our planet. The first emissions device to be installed on an internal combustion motor by mandate with the idea of cleaning up the air was in 1967. This was followed by the removal of tetraethyl lead from fuel following the 1973 Arab Oil Embargo. The only fuel we had to run at that time was unleaded 87 and you had to sit in line to get it. Many times, the station would run out of fuel when you were sitting in line waiting your turn to fill up. Many days, the stations would put signs out, stating that they had no fuel to sell that day.

Anyway, lead was removed from fuels because of the damage to the planet.
These photos of Los Angeles air quality will show you why something had to be done......
https://www.google.com/search?hl=en&...w=1264&bih=710
Without some substance in the fuel to dirty-up the seats, reversion was once again a factor in internal combustion engines. The only real fix was to install hardened exhaust valve seats into grooves machined into the heads.

Down through the years, other fellows have advised me that adding half a quart of regular petroleum-based automatic transmission fluid to a tank of gas will help to dirty the seats enough to prevent welding. I don't know if that's legal or not, probably not, although I have done it in the past.

I hope I have been able to make sense of this to you.

Last edited by techinspector1; 05-04-2013 at 04:24 PM.
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Old 05-04-2013, 04:52 PM
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A lot of rodders and restorers have used Marvel Mystery Oil as a gas additive and oil additive and claim it is protecting their vintage engines and swear by it.
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Old 05-04-2013, 05:49 PM
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valve seat life

lead was aded to fuel as a octain booster,as compression grew from 6 to1 to 10 to1or more. lead side effect its also a lubricant of sorts that stoped valve seat problems.it was removed when the emisions became a issue as the lead fowled the catelitic converter.as a hoby builder i just leave a slightly wider seat and throw in some 2cycle oil.every other tank full
tho i am sure the hardend seats are the best way,especially on a engine that is worked hard and 1 wants good life. for most older restoes they never put enough miles to show a problem.some time in the 70es ford and gm hardend the seats in the cast heads. ok for the first go,but the hardnes was shallo and was removed first valve job. my info comes from a seminar put on years ago by standerd oil the vave seat isue is i do all my own valve work and some for frends,with old equ. no machine shop would use to day
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Old 05-04-2013, 05:55 PM
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That said; the true story behind TEL was to reduce the volatility, and slow the burn rate, and prevent detonation (spark knock)
in "high compression" engines, some time back in the late '20's early '30's. Other than that, it only caused problems with fouled plugs, and sticky valves, if it wasn't "scavenged", or burned off enough, by.... guess what, High combustion temps.
So, leaded fuel had to ignite at a higher temp, and burn hotter in order to prevent "lead fouling" of the plugs and valve train. So when Unleaded fuel was invented, there had to be some way of raising the ignition temp, yet slowing the flame front, in order to prevent "spark knock". (IOW keep the same octane rating) Now in this day and time, fuel at the pump burns so cold, that any lead added to it would cause more trouble than it's worth. Ethanol, by it's nature produces fewer BTUs than the same amount of gasoline. So gas infused with 10% ethanol, burns cooler than gas without, add to the equation TEL, and you get a formula for tuneups every thousand miles or less. and the need for valve jobs etc. due to lead fouling.
Why izzit that the average off the shelf chevy V-8 Oh, say a 5.0 of '87 vintage that has been running on unleaded fuel all it's life can go over 200k miles with nothing but oil change. And LOOK it has cast iron heads, with valve seats ground directly into the head, not special hard seats drilled, and swaged into the head. Or mabe my old Ford with cast iron heads and seats, that have been running on unleaded since 1976, and I did a half assed valvejob on them about 150k miles ago.

Now I have some other experiences with leaded fuel. more recent.
As some of you might have guessed by now, I also play with airplanes. At the airport the only fuel available is 100LL. which is 100 octane leaded fuel. It causes a lot of problems, with lead fouling.
"Certified" (production aircraft) must use that fuel, But, they can get permission to use "MOGAS" (car fuel) available at any gas station anywhere, as long as it does not contain ethanol.
And the "experimentals" (not production, equivilant to hot rod) can burn whatever gas they want to.
Same engine, the experimentals last longer due to running car gas, than the certified running leaded 100LL. I have experience with both, and found that unleaded car gas, will extend the life of engine, way beyond the same engine burning leaded fuel. And will reduce Maintenance cost, by not having lead fouled components.
The average aircraft engine is not very different than an automobile engine of the 40's, in the material that it's constructed of. albeit weight has been saved where it can be. so you get a 360 cubic inch 4 cylinder, with aluminum case, instead of a cast iron V-8. But still have cast iron seats, and mabe stainless, or sodium filled valves. but that's 1930's technology. And they hold up very well with unleaded car gas.
Why should a set of heads from 1969 not hold up after overhaul, at least 1/2 as good as they did new?
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Old 05-04-2013, 07:01 PM
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If you had all this data in your memory banks, why did you come trolling here with questions?
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Old 05-05-2013, 08:05 AM
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It is all about valve spring pressure. You can use unleaded gasoline without any problems if you keep valve spring pressure less than 120 - 125 lb on the seats. If you have a camshaft that requires more valve spring pressure than 125 lb. you will shorten the exhaust valve seat life. To avoid that problem when using a high-lift camshaft that requires over 125 lb. valve spring seat pressure, you should install hardened exhaust valve seat inserts.

In 1972, GM recognized the problem and started using induction hardened exhaust valve seats in the 1973 production year. The GM bean counters only allowed hardened exhaust valve seat inserts mto be used in the low production industrial and some truck engines due to the extra machining operations and extra cost. The GM engineers knew that induction hardened exhaust valve seats was a temporary solution so in the 1975 production year, when high performance engines were finally a thing of the past, GM reduced valve spring pressure and installed low lift camshafts and eliminated the induction hardened exhaust valve seats in cast iron heads. I was told that the 2006 LS engine have induction hardened exhaust seats or hardened seat inserts.

Last edited by MouseFink; 05-05-2013 at 08:13 AM.
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Old 05-05-2013, 09:43 AM
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If you had all this data in your memory banks, why did you come trolling here with questions?
lookin' for something I might have missed is all.

I think MouseFink may be on to something with spring pressures.

and as this is not a high compression, high power, radical cam engine, there would be no reason to increase spring pressures.
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Old 05-05-2013, 10:07 AM
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st3gamefarm
an aircraft engine usually has a maximum RPM around 2700 except a few with PSRUs.The CR is very low in lycomings/continentals ...The plugs foul very quickly when using 100LL. The LL part of the formula is not really accurate as it has more lead than cars ever had from pump gas. The "STC" to use mogas in an airplane usually requires some mods to the A/C engine,except ,,example only,, the cessna 150s only got a sticker,no mods at all to the aircraft.
The 100/150 hp A/C engines were designed to run on 87 octane aircraft fuel. Aircraft need other additives in their fuel that mogas does not have,thats why an STC is required.
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Old 05-07-2013, 09:24 AM
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Lead was used as an anti-knock agent and as a high temp lubricant to prevent valve seat recession into the heads. When Chev was doing testing back in 1971. Over night Chev. engineers were told by Ed Cole to "Get the lead out"
In standard 200 hour full power dyno tests of Big Block Chev engines, you might see 0.025"-0.030" of valve recession with leaded gas, with unleaded gas, you the heads were done after only 25 hours. This directly led to the "induction hardened valev seat". An electric inductor was brough into proximity of teh seat and it heats teh seat cherry red, then it is quenched. This fixed teh issue of valve receding valve seats and is still in use today.

You can see the heat marking across the cyclinder head combustion chamber around this induction hardened Vortec L31 exhaust seat.


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hog
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Old 05-11-2013, 05:38 AM
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Hogg.Actually the tests where set up for one hr at 1,500 and one hr at 4,000 24/7.The failure rate time came in at 22.75hrs.
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Old 05-11-2013, 09:01 AM
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Hogg.Actually the tests where set up for one hr at 1,500 and one hr at 4,000 24/7.The failure rate time came in at 22.75hrs.
Only reporting what I was told. The engine were at "full power" or at WOT, the engine rpm was usually cycled between peak torque and peak power. Are you talking about 454 testing?

The reason that all BBC'swent with induction hardened valves was because Chev didnt think it could source enough nickle for every engine. So they induction hardened the all BBC's but the truck BBC's, these engine got the inserts.


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Old 05-11-2013, 11:40 AM
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I was "the guy" in the dyno rm at the Tonn,NY Engine plant.One of the jobs I did when there.Odd that I remembered that after all these yrs.It's just one thing that stuck in my mind I guess.
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